1. Field of the Invention
The present invention provides peptides and compounds that bind to receptors which contain at least one of the .alpha., .beta. or .gamma. IL-2 receptor subunits. The invention has application in the fields of biochemistry and medicinal chemistry. In particular, the present invention provides IL-2 inhibitors for use in the treatment of human disease.
2. Description of Related Art
Immunology has experienced rapid advances throughout the past decade, especially in the determination of the mechanisms by which the immune system is activated and regulated. Development of successful models for immunologic regulation is an important scientific objective, given the critical role of such regulation in the body's inflammatory response and in pathologic conditions such as lupus, AIDS, and cancer. The development of new techniques for organ transplantation has also created a major demand for immunosuppressive drugs to forestall foreign tissue rejection.
One area of major activity with regards to immune system regulation involves lymphokines. These substances were discovered in the mid- 1960s when Norwell noted that plant lectins were mitogenic for lymphocytes. However, it was not until a decade later, when techniques for culturing T-cells for prolonged periods became available, that interest in this area developed with the discovery that IL-2 is a central component for T-cell proliferation. This realization led to the discovery of the IL-2 receptor (IL-2R), the activation of which, by IL-2, was shown to be the signal for T-cell division (see INTERLEUKIN-2, Kendall Smith ed., pp. 1-6, Academic Press (1988), which is incorporated herein by reference).
Three classes of IL-2 receptors have been identified. The high-affinity receptor (K.sub.D =10.sup.-11 M) contains three subunits: IL-2R.alpha., IL-2R.beta. and IL-2R.gamma.. An intermediate-affinity receptor (K.sub.D =10.sup.-9 M) comprises the IL-2R.beta. and IL-2R.gamma. subunits. In contrast, the IL-2.alpha. subunit binds IL-2 with low affinity (K.sub.D =10.sup.-8 M). (Minami, et al., Ann Rev. Immunol., 11:245-267 (1993), which is incorporated herein by reference.)
IL-2R.alpha. has a molecular weight of about 55 kD, but is not a constituent of resting cells. Rather, the expression of IL-2R.alpha. is induced by a variety of factors, including antigen, phorbol esters, mitogenic lectins, TNF-.alpha. and the tax protein of HTLV-1 (Ballard, et al., THE MOLECULAR ASPECTS OF AUTOIMMUNITY, p. 227, Academic Press (1990); and Paul, PRINCIPLES OF IMMUNOLOGY (Raven Press 1992), both of which are incorporated herein by reference). IL-2R.beta. is a glycoprotein having a molecular weight of about 70 kD and is a constituent of resting T and NK cell surfaces. In addition, it has been shown that the .beta. subunit is indispensable for signal transduction (see EP 539,748 A1 to Shimamura, et al.) It has been suggested that the .alpha. subunit controls primarily association while the .beta. subunit regulates ligand dissociation (see Ballard, et al.) The .gamma. subunit is believed to augment binding by the .beta. subunit as well as have a role in signal transduction. The gene coding for IL-2R.gamma. has been placed into a vector and successfully transfected into cells to render them capable of producing IL-2R.gamma. (see, Sugamura, et al., European Patent Application No. 578,932 A2, which is incorporated herein by reference). An assay for the detection of the gene and an antibody for immune response regulation based on the IL-2R.gamma. chain are also described by Sugamura, et al.
Because of the .gamma. subunit's multi-faceted role in regulating the response of immune cells to stimulation, both as a signal transducer and binding agent, there have been efforts to control the immune response through blocking the IL-2/IL-2R.beta. interaction. For example, EP 539,748 A1 to Shimamura, et al. describes the production of polypeptides capable of competitively binding to IL-2R.beta.. These polypeptides are characterized by having about 240 residues and containing a functional antibody V-region capable of selectively inhibiting the binding of IL-2 to the .beta. subunit. Others have focused on developing antibodies to the .alpha. subunit and IL-2 analogs (see, e.g., U.S. Pat. No. 5,229,109 to Grimm, et al.)
Recently, the .gamma. subunit has been implicated in the regulation of IL-4, IL-7 and possibly IL-13 as well as IL-2 (see, Science, 262:1818 (1993); Kondo; and Russell, et al., Science, 262: 1880-1883 (1993), each of which is incorporated herein by reference). With respect to IL-4, the .gamma. subunit may be a component of a heterodimer which enhances the affinity of IL-4 binding in a fashion similar to IL-2 as just described. The implication of the .gamma. subunit in the regulation of IL-2 and IL-4 indicates that the .gamma. subunit is a pivotal component in T and B cell development. Defective .gamma. subunit production has been identified as a key factor in X-linked severe combined immunodeficiency disease (XSCID, commonly known as the "bubble boy disease"). IL-4 has also been implicated recently in the stimulation of B-cells and mast cells, in particular stimulating the differentiation of B-cells to produce IgE. Thus IL-4 is a promising candidate for use as an antiviral, antibacterial and anticancer drug. Additionally, IL-4 has been identified as a possible treatment for Kaposi's Sarcoma, which is considered to be the most deadly complication associated with AIDS (Biotechnology News 14:4-5 (Feb. 11, 1994), incorporated herein by reference). The .gamma. subunit has also been linked to a high affinity IL-7 receptor dimer (Noguchi, et al., Science, 262: 1877-1880 (1993), incorporated herein by reference), further implicating this particular subunit in the regulation of thymocyte development. Also, the IL-2R.gamma. and IL-2R.beta. subunits have been proposed as having binding affinity for the recently discovered IL-15 cytokine (Science, 264:965-967 (1994), incorporated herein by reference).
The availability of recombinant receptor proteins allows for the study of receptor-ligand interaction in a variety of random and semi-random peptide diversity generation systems. These systems include the "peptides on plasmids" system described in U.S. patent application Ser. No. 963,321 filed Oct. 15, 1992, which is a continuation-in-part of U.S. Pat. No. 5,270,170, the "peptides-on-phage" system described in U.S. patent application Ser. No. 718,577, filed Jun. 20, 1991, and in Cwirla et al., Aug. 1990, Proc. Natl. Acad. Sci. USA 87:6378-6382, the "encoded synthetic library" (ESL) system described in U.S. patent application Ser. No. 946,239, filed Sep. 16, 1992, which is a continuation-in-part of Ser. No. 762,522, filed Sep. 18, 1991, and the "Very Large Scale Immobilized Polymer Synthesis" system described in U.S. Pat. No. 5,143,854; PCT patent publication No. 90/15070, published Dec. 13, 1990; U.S. patent application Ser. No. 624,120, filed Dec. 6, 1990; Fodor et al., 15 Feb. 1991, Science 251:767-773; Dower and Fodor, 1991, Ann. Rep. Med. Chem. 26:271-180; and U.S. patent application Ser. No. 805,727, filed Dec. 6, 1991. Each of the foregoing patent applications and publications is incorporated herein by reference.
Thus, there remains a need for non-toxic compounds that bind to or otherwise interact with IL-2, IL4, IL-7 and IL-13 receptors with high affinity, both for studies of the important biological activities mediated by this receptor and for treatment of disease. The present invention provides such compounds.